Embossed or dimpled combined board

ABSTRACT

A method and apparatus for making an embossed or dimpled combined board is disclosed. The combined board has two outer or facing layers or webs of paperboard which sandwich an embossed or dimpled middle paperboard layer or web. The middle web is embossed by passing it over two apertured vacuum drums. Embossments extending in one direction are vacuum formed on one surface of the middle web by the first vacuum drum, while embossments extending in the opposite direction are formed on the other surface of the middle web by the second vacuum drum. The embossments, i.e., concave and convex impressions, are located in a generally chess board pattern. The vacuum openings or apertures of the second drum are larger (larger average diameter) than those of the first drum, to thereby compensate for diminishing flexibility of the middle web due to drying as it passes sequentially over the first and second vacuum drums. This vacuum opening size difference permits the formation of embossments of equal height on both surfaces of the middle web. Preferably each of the three webs are fed directly from a paperboard making apparatus and the combined board formed prior to final drying of the webs. Alternatively, the middle web may be wetted if already fully or partially dried prior to forming the embossments. While being deformed by the vacuum drums, an external source of heat or radiation, such as steam, hot air, infrared lamps, or the like, may be directed to the web such that the web is concurrently dried as it is being deformed to form the embossments or dimples.

BACKGROUND OF THE INVENTION

This invention relates to a method and apparatus for the formation of alaminate web of indefinite length, the laminate characterized by twoouter or facing paperboard webs which are adhered to and sandwich amiddle embossed or dimpled paperboard web. Such laminates are useful formaking paperboard boxes.

It is known to form a three layer combined board or three layer laminatefrom two outer or facing layers and an inner undulating or corrugatedlayer. Sometimes the inner layer is corrugated and assumes the generalform of a sine wave, or assumes the form of dimples, with the dimpleseither extending outwardly from one side only of the middle layer, oroutwardly from both sides. However, the formation of such a combinedboard or laminate having embossments or dimples extending on both sidesis difficult to carry out. A basic manufacturing problem is that ofdrying of the middle layer as it is being deformed, i.e., as the dimplesor corrugations are formed. In the case of vacuum drum deformation,wherein one or more vacuum drums having apertures on their respectivesurfaces would be employed, the drying of the paperboard as it is beingdeformed into the drum apertures would present a problem, namely, thelack of desired flexibility and ductility of the paperboard to therebypermit deformation into dimples or embossments having the same height.This problem would become more accentuated wherein one vacuum drum wasused to provide dimples or embossments on one surface of the web, whilea second vacuum drum was used to form embossments on the other surface.During the formation of the first group or set of embossments, thepaperboard would be dried out by the passage of air through it, due tothe vacuum formation process, i.e., the porous character of thepaperboard. By the time the paperboard reached the second vacuum drum,the paperboard would be significantly dried and is hence even lessflexible and thereby more difficult to deform and hence more apt to tearor rip.

SUMMARY OF THE INVENTION

According to the practice of this invention, an embossed or dimpledcombined paperboard is formed having the usual two smooth, outer facinglayers. The middle layer is formed by passing one surface thereof overan annular portion of a first vacuum drum having a plurality of vacuumapertures or openings over its circumferential side. This causes thepaperboard web, after leaving the first vacuum drum, to have embossmentsor dimples extending from one surface thereof. This same paperboard webis now passed to a second vacuum drum also having a plurality of vacuumapertures over its circumference, and the process repeated. In order tocompensate for less flexibility of the paperboard by the time it reachesthe second vacuum drum due to drying, the vacuum openings on the secondvacuum drum are made larger than those of the first. This permits theless flexible paperboard web, after it leaves the first vacuum drum, toundergo the desired amount of deformation, to obtain embossments ofequal height, without tearing or ripping of the second embossmentsformed by the second vacuum drum and which extend from the other surfaceof the middle layer or web. Thereafter, the three layer laminate isformed as by conventionally gluing the two facing webs onto the tops ofthe dimples on respective sides of the middle, embossed paperboard webor layer.

The invention may be carried out by wetting an already dried orpartially dried paperboard web which is to form the middle layer andthen passing it to the two vacuum rolls having different size vacuumopenings, after which it is formed to a three-layer laminate. Preferablyhowever, the method of this invention is carried out by feeding allthree of the webs which are to form the three layer combined boarddirectly from the respective paperboard making apparatus which forms therespective individual webs. In this manner, the completed product isformed prior to final web drying, thus obviating the requirement forwetting or re-wetting the middle layer prior to its deformation on thetwo vacuum drums. Alternatively, the middle layer may be fed to thevacuum drums directly from a paperboard making apparatus, before finaldrying, while the two facing layers fed from rolls of already dried orpartially dried paperboard webs. The middle layer undergoes moredeformation than the facing layers, hence it should be as flexible orductile as possible.

Although not the preferred method of carrying out the invention, thevacuum openings in both vacuum drums may be of the same size, i.e., ofthe same average diameter. Such an arrangement may be employed whenfabricating embossed paperboard from relatively thin webs which are ableto withstand relatively greater deformation without tearing than morecommon paperboard webs of greater thickness when forming the second setof embossments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a complete installation forcarrying out the invention in its preferred form, and shows threedistinct paperboard making machines or apparatus for forming each of thethree webs required to make the final combined board product.

FIG. 2 is a view similar to FIG. 1, but illustrates the formation of thecombined board of this invention from paperboard webs which have alreadybeen dried.

FIG. 3 is a typical longitudinal cross section of the embossed ordimpled combined board of this invention.

FIG. 4 is a partial schematic view of the first vacuum drum, the drumprovided with circular vacuum openings.

FIG. 5 is a partial schematic view of the second vacuum drum, showinglarger circular openings than those of the first vacuum drum.

FIG. 6 is a partial schematic view of the first vacuum drum, accordingto a modification, similar to FIG. 4, showing elongated, rectangularvacuum openings in the first vacuum drum, as opposed to circularopenings.

FIG. 7 is a partial schematic view of the second vacuum drum, accordingto a modification, showing larger elongated, rectangular vacuum openingsthan those of the first vacuum drum.

FIG. 8 is a partial plan view of the middle web of the laminate, whereinthe middle web has been deformed by vacuum drums having differentlyshaped vacuum openings on their respective circumferential sides toproduce differently shaped embossments

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIG. 1 of the drawings, an installation for carryingout the present invention is schematically illustrated. The numeral 10denotes a first paperboard manufacturing apparatus for producing a webof paperboard of indefinite length. The numeral 12 schematicallydesignates a conventional head box, with numeral 14 schematicallydesignating the conventional Fourdrinier belt or wire, with 16 denotingconventional rollers, which may include rollers such as drying rollers,and other conventional apparatus downstream of the head box and belt,all for producing a paperboard web 18 of indefinite length. It will beunderstood that any particular paperboard making apparatus 10 may beemployed. Web 18 will form one of the two facing webs of the finishedproduct, the latter to be described. An adhesive applying station orapparatus is schematically designated by 20 for affixing glue to theinner surface of web 18. From this station, web 18 passes over aconventional roller or roller assembly 22 for pressing web 18 onto themiddle web of the three layer board.

Again referring to FIG. 1, the numeral 30 denotes a second paperboardweb making apparatus or machine which also typically includes a head box32 and Fourdrinier wire 34. Numeral 36 denotes conventional downstreamroll or drum web treating means of the second apparatus 30, which mayinclude drying and other rollers, all for producing a paperboard web ofindefinite length. One surface of web 38 is passed over a first rotatingvacuum cylinder or drum 42 having a plurality of vacuum openings orapertures on its circumferential surface. After leaving the first vacuumdrum 42, web 38 (now provided with embossments or dimples extendingsubstantially normally from one surface thereof) is passed to a secondrotating vacuum drum 44 also having a plurality of vacuum openings onits surface. Vacuum drum 44 produces embossments or dimples on the otherside of web 38, also extending substantially normally from web 36. Thevacuum openings of drum 44 are larger in average diameter than those ofdrum 42. The vacuum openings on drums 42 and 44 and the drums are soarranged that the second vacuum drum produces embossments only betweenthe embossments made by the first drum, i.e., a chessboard pattern isformed. Heating elements 43 are located contiguous to the web contactingsurfaces of vacuum drums 42 and 44, and may consist of infrared lamps,hot air or steam producing devices, dielectric heaters, or otherconventional heating means, the exact nature and construction of whichare not material to the invention. Such heating of the web as theembossments are being formed enhances the strength of the embossments.Any conventional mechanism (not shown) for providing coordination of therotation of the two drums may be used. Typically, the centers of the twodrums are 8-30 feet apart. The time taken for web 38 to exit from thefirst drum and initially contact the second drum is typically between0.2-0.5 seconds, Prior to contacting first drum 42, web 38 typicallycontains 40-60% dry solids. Web 38 is to form the middle layer of thecompleted combined board of this invention.

A third paperboard making apparatus or machine is designated in FIG. 1as 50, and includes, typically, a head box 52 and Fourdrinier wire 54,together with conventional downstream elements 56, which may includedrying and other rolls, for forming the second outer or facingpaperboard web 58. An adhesive applying apparatus or rotation isschematically designated as 60 and applies glue to the inner surface ofweb 58. The lower facing web 38 is also applied at station 22.

Facer webs 18 and 58 are dried to a dryness of about 80-90 percent by arespective web contacting means 16 and 56, while web 38 is dried bymeans 36 to about 50 percent dryness.

Referring now to FIG. 2 of the drawings, an apparatus or installationfor forming the product of this invention is illustrated wherein thethree paperboard webs are fed from already dried or partially dried websof paperboard wound on rolls. A roll of dried paperboard is indicatedschematically as 66, with middle layer 38 of the paperboard beingunwound therefrom. Wetting or spray stations are schematicallydesignated as 70 to impart added moisture to the dried paperboard.Feeding mechanisms which may include drying rollers are schematicallydesignated as 72 to feed middle paperboard web 38 to first vacuumcylinder 42 from whence it unwinds and is then fed to second vacuumcylinder 44, these being the same rotating, apertured vacuum cylindersor drums as partially schematically indicated as FIG. 1. Similarly, topor upper paperboard web facing 18 is drawn from a first dried orpartially dried web roll 76, while the other facing layer 58 is drawnfrom dried or partially dried web roll 80, the webs from these rollsalso optionally being contacted by conventional rolls. The three webs18, 38, and 58 are fed to a forming station which includes rotatingrolls 22 which were also shown at FIG. 1. At this station, thecorrugated or dimpled three layer product of this invention is assembledby conventional apparatus. This method is useful for producing adecorative laminate where strength is not important, the method alsoemploying the above mentioned advantages yielded by the larger vacuumopenings on the second vacuum roll.

Referring now to FIG. 3 of the drawings, a typical longitudinal crosssection of the completed, combined paperboard laminate of this inventionis illustrated. Again, the top or outer facing web is designated as 18while the lower web is designated at 58, with the middle layer 38 shownas including a plurality of oppositely directed dimples or embossments.Each of one set of generally conical embossments is designated as 90 andextends upwardly from one surface of web 38, with each of the other setof generally conical embossments denoted as 92 and extending downwardly,from the other surface of web 38. The tips of upper embossments 90 areglued as indicated at 91 to top facing layer 18, with the tips ofdownwardly extending embossments 92 glued to facer web 58 as indicatedby 93. It will be observed that the diameter 96 of embossments 90 isless than the diameter 98 of embossments 92, the latter having beenformed by the second rotary vacuum drum 44 of FIGS. 1 and 2. Thediameter of the embossments refers to their average base diameter, i.e.,where the embossments commence to project from the middle web 38. Theheight or depth of embossments 90 is designated as 100 while the heightor depth of embossments 92 is designated as 102. It will be seen fromFIG. 3 that heights 100 and 102 are equal, although they need not be so.The greater diameter 98 of embossments 92, as compared with diameter 96of embossments 90, is caused by the greater size of the vacuum apertureson second rotating vacuum drum 44 as opposed to the size of the vacuumapertures on first rotating vacuum drum 42. The dimples 90 and 92 aretypically arranged, in a plan view of the middle web 38, in a chessboard pattern (see FIG. 8).

FIGS. 4 and 5 show the differing diameters between vacuum openings 100of first drum 44 and (larger) vacuum openings 102 of second drum 44. Thedashed circles 102 of FIG. 4 illustrate that openings 102 of drum 44 arestaggered with respect to vacuum openings 100 of drum 42 at the nipbetween these two rolls, so that the embossments of the completelydeformed web 38 form a chessboard or checkerboard pattern.

FIG. 6 shows first vacuum drum 42 provided with elongated, rectangularvacuum openings 106, which are smaller than vacuum openings 108 onsecond drum 44 of FIG. 7. Either the width or the length or both ofslots 106 is smaller than that of slots 108. Slots 10 may also extendthe entire length of the vacuum drums. In the latter case, the shape ofweb 38 after passing around both vacuum drums will approximate that of asine wave such as that of a conventional middle liner corrugated layerproduced by passing a web through the nip of two gear wheel like drumsor cylinders. It will be understood that the peripheral shape of theopenings in the two vacuum drums may also be triangular, square,ellipsoidal, or of any desired form. Further, the embossments 90 on onesurface of web 38 may be of a different shape than those 92 on theopposite surface of web 38 (again see FIG. 8). For example, the vacuumopenings in the first vacuum drum 42 may be round such as those shown atFIG. 4 by 100, while the larger vacuum openings in the second drum 44may be rectangular, such as those shown in FIG. 7 and denoted as 108.The dashed rectangles 108 of FIG. 6 show their staggering with respectto openings 106 of drum 42 at the nip between rolls 42 and 44 of FIGS. 6and 7, so that the embossments of the completely deformed web 38 form achess board pattern.

FIG. 8 illustrates the middle web 38 which has been deformed by onevacuum drum having circular openings in its circumferential face, suchas drum 42 of FIG. 4, and by another vacuum drum having rectangularopenings in its circumferential face, such as drum 44 of FIG. 7. A chessboard pattern is maintained, i.e., next adjacent dimples in the rows andcolumns of deformed web 38 extend in opposite directions. Rectangularembossments 108 extend downwardly, while circular embossments 100 extendupwardly, toward the reader.

Typical vacuum openings on first drum 42 are from 2 to 5 mm in averagediameter (size), while vacuum openings on second drum 44 are from 3 to 6mm in average diameter (size). The thickness of the paperboard webs istypically 0.2 to 0.4 mm. Ambient air temperature is typically up to 600°F., while the vacuum in drums 42 and 44 is typically up to 8 psi (belowatmospheric), with drum diameters typically 2 to 10 feet.

While the embossed or middle layer 38 is usually covered on both of itsdimpled faces with flat facing webs 18 and 58, the latter secured byrespective adhesive areas 91 and 93 to the tips of the embossments ordimples, only one of the facing webs 18 or 58 may be employed to producean embossed web of only two layers, one being flat and the other beingdimpled or embossed.

The invention has been described in connection with forming an embossedpaperboard web of indefinite length, since this is the manner in whichcommercial quantities are produced. However, it will be immediatelyapparent that selected webs of fixed lengths may be employed using themethod disclosed herein.

We claim:
 1. A method of making an embossed paperboard web of indefinitelength, the method including the steps of, continuously feeding apaperboard web of indefinite length and having two opposite surfaces toa first rotating vacuum drum, said first rotating vacuum drum having aplurality of vacuum openings on its surface, one surface of saidpaperboard web passing in surface contact with and over a limitedannular portion of said first vacuum drum, to thereby form a first setof embossments on one side of said web by said web being partially drawninto said vacuum openings and deformed, feeding the opposite surface ofsaid web, after the web leaves said first drum, to and over a limitedangular extent of a second rotating vacuum drum, said second vacuum drumhaving a plurality of vacuum openings on its surface, to thereby form asecond set of embossments on the other side of said web, said openingson said second vacuum drum being larger then said openings on said firstvacuum drum, to thereby produce an embossed paperboard web havingdiscrete convex embossments on both surfaces thereof.
 2. The method ofclaim 1 including the additional concurrent steps of continuouslyadhering a first paperboard facing web portion, from a first paperboardfacing web of indefinite length, to the tips of the embossments of aportion of one surface of said embossed web, and continuously adhering asecond paperboard facing web portion, from a second paperboard facingweb of indefinite length, to the tips of the embossments of a portion ofthe other surface of said embossed paperboard web, to thereby produce athree layer laminated paperboard.
 3. The method of claim 1 wherein saidvacuum openings on said drums are annular and wherein the diameter ofsaid annular openings of said second drum is greater than the diameterof said annular openings of said first drum.
 4. The method of claim 1wherein said vacuum openings on said first and second drums areelongated slots and wherein the width of said slots of said second drumis greater than the width of said slots on said first drum.
 5. Themethod of claim 4 wherein said slots of said drums rum substantiallytransversely of said embossed web.
 6. The method of claim 1 wherein saidpaperboard web which is embossed is fed directly from a paperboardmaking apparatus prior to final drying of the paperboard web, wherebysaid embossments are formed prior to final drying of said paperboardweb.
 7. The method of claim 2 wherein said paperboard web which isembossed is fed directly from a paperboard making apparatus prior tofinal drying of the paperboard web, whereby said embossments are formedprior to final drying of said embossed paperboard web, and wherein saidfirst and second paperboard facing webs are both fed directly fromrespective paperboard making apparatus prior to final drying of saidpaperboard facing webs.
 8. The method of claim 1 including the step ofheating said web as it passes in surface contact with at least one ofsaid two vacuum drums, whereby said web is embossed and dried during theapplication of externally supplied heat energy and the strength of theembossments is increased by such concurrent drying and deforming.
 9. Amethod of making an embossed paperboard web of indefinite length, themethod including the steps of, continuously feeding a paperboard web ofindefinite length and having two opposite surfaces to a first rotatingvacuum drum, said first rotating vacuum drum having a plurality ofvacuum openings on its surface, one surface of said paperboard webpassing in surface contact with and over a limited annular portion ofsaid first vacuum drum, to thereby form a first set of embossments onone side of said web by said web being partially drawn into said vacuumopenings and deformed, feeding the opposite surface of said web, afterthe web leaves said first drum, to and over a limited angular extent ofa second rotating vacuum drum, said second vacuum drum having aplurality of vacuum openings on its surface, to thereby form a secondset of embossments on the other side of said web to thereby produce anembossed paperboard web having discrete convex embossments on bothsurfaces thereof.
 10. The method of claim 9 including the additionalconcurrent steps of continuously adhering a first paperboard facing webportion, from a first paperboard facing web of indefinite length, to thetips of the embossments of a portion of one surface of said embossedweb, and continuously adhering a second paperboard facing web portion,from a second paperboard facing web of indefinite length, to the tips ofthe embossments of a portion of the other surface of said embossedpaperboard web, to thereby produce a three layer laminated paperboard.11. The method of claim 9 wherein said vacuum openings on said drums areannular and wherein the diameter of said annular openings of said seconddrum is greater than the diameter of said annular openings of said firstdrum.
 12. The method of claim 9 wherein said vacuum openings on saidfirst and second drums are elongated slots and wherein the width of saidslots of said second drum is greater than the width of said slots onsaid first drum.
 13. The method of claim 9 wherein said slots of saiddrums rum substantially transversely of said embossed web.
 14. Themethod of claim 9 wherein said paperboard web which is embossed is feddirectly from a paperboard making apparatus prior to final drying of thepaperboard web, whereby said embossments are formed prior to finaldrying of said paperboard web.
 15. The method of claim 10 wherein saidpaperboard web which is embossed is fed directly from a paperboardmaking apparatus prior to final drying of the paperboard web, wherebysaid embossments are formed prior to final drying of said embossedpaperboard web, and wherein said first and second paperboard facing websare both fed directly from respective paperboard making apparatus priorto final drying of said paperboard facing webs.
 16. The method of claim9 including the step of heating said web as it passes in surface contactwith at least one of said two vacuum drums, whereby said web is embossedand dried during the application of externally supplied heat energy andthe strength of the embossments is increased by such concurrent dryingand deforming.